ABSTRACT

INTRODUCTION In clinical therapy, topical application allows localized drug delivery to the site of interest. This enhances the therapeutic effect of the drug while minimizing systemic side effects. Furthermore, topical application of drugs bypasses systemic deactivation or degradation and minimizes gastrointestinal incompatibility and potential toxicological risk. Several physical and chemical methods with varying degrees of effectiveness have been devised. Physical methods have the advantage of decreased skin irritation or allergic responses. Among the physical methods under development or investigation are iontophoresis, electroporation, jet injectors, microneedles, and application of ultrasound and pressure waves (PWs) (see Chapter 1). In this chapter, we review ultrasound and PWs and discuss their applications for drug delivery. Both methods exert mechanical forces on the stratum corneum (SC), the topmost dead layer of skin, which is responsible for the skin’s barrier properties. Furthermore, their mechanisms of permeabilization, in terms of effect on skin structure, also appear to be similar.